This application is for funds to purchase a BD Biosciences Special Order LSRII quadruple-laser FACS analyzer that will be situated in the new Cytometry and Cell Sorting Core at Baylor College of Medicine (BCM). This instrument has been selected to serve the purposes of over 16 investigators involved in over 18 NIH- funded projects. This instrument has been designed to serve two key purposes in our community. First, many BCM investigators require the capacity to analyze on multiple fluorescent markers concomitantly with multiple cell surface markers. Our four-laser instrument will allow analysis based on multiple parameters simultaneously such as mCherry, cyan fluorescent protein, yellow fluorescent protein, and allophycocyanin (APC) or sytox red. It will have a 561-nm solid-state laser, allowing detection of red fluorescent protein derivatives such as mCherry and increasing the sensitivity of detecting commonly used probes such as phycoerythrin. It will also be equipped with a 405-nm solid-state laser enabling the use of violet sensitive probes including cyan fluorescent protein and the fluorochrome Pacific Blue. Additionally, a 640-nm laser will allow detection of fluorochromes such as APC and its conjugates as well as the viability dye sytox red, which will give added power and flexibility to all investigators needing multiple easy-to-use parameters for analysis. Finally, the instrument will be equipped with a 488-nm solid-state laser enabling detection of standard fluorophores including green fluorescent protein, yellow fluorescent protein and fluorescein. The second key purpose for this flow analyzer is small-particle detection to study bacteria and yeast, which is critical for four groups of investigators at BCM. Thus, the instrument will include a forward scatter photo-multiplier tube detector enabling small particle detection and analysis, directly enhancing the research using bacteria and yeast. This instrument will afford maximum capabilities as well as maximum flexibility to best serve the evolving needs of the diverse BCM investigators and Texas Medical Center research community. This instrument is essential for the broad base of health-related research at BCM, including projects aimed at developing new therapies in regenerative medicine, cancer, HIV/AIDS, immunology and aging, which will contribute to the overall wellness of our society. Public Health Relevance: Our research at the Baylor College of Medicine requiring a four-laser LSRII flow cytometer will specifically study processes within cells allowing us to better understand stem cell therapies, aging processes, cancer biology and cardiovascular development. The requested LSRII flow cytometer is critical for determining the complexity and differences between individual cells, which is essential for our research projects aimed at developing new treatments or cures for serious human illnesses including cancer, heart abnormalities, stroke and HIV/AIDS.